1. Field of the Invention
This invention relates generally to semiconductor device packaging, and more particularly to a dicing method of semiconductor devices package for dividing a wafer or panel into discrete package.
2. Description of the Prior Art
In the electronic component world, integrated circuits (IC's) are typically fabricated on a semiconductor substrate, known as a chip, and most commonly are made of silicon. The silicon chip is typically assembled into a larger package, which serves to provide effective enlargement of the distance or pitch between input/output contacts of the silicon making it suitable for attachment to a printed circuit board, and to protect the IC from mechanical and environmental damage.
Conventionally, ICs are packaged one by one after dicing from a wafer. A wafer level package (WLP) or a chip scale package (CSP) was developed to provide an alternative solution to directly attached flip chips devices, and plurality of dice are separated into individual devices after they are packaged. Die separation, or dicing, by sawing is the process of cutting a semiconductor substrate into its individual die. Wafer dicing technology has progressed rapidly to satisfy every packaging requirement, such as high throughput, high yield and low cost.
As shown in FIG. 1, it is a side view of plurality of flip chip devices 100 in a wafer according to prior art. The flip chip 100 comprises a die 105 with metal pads 106 that typically has a conventionally fabricated IC device structure. A buffer layer 103 is formed on a substrate 102 and adjacent to the die 105. The die 105 is adhered on the substrate 102 through an adhesive layer 104, and the die 105 has a plurality of electrical connections 108, such as redistribution layer (RDL) trace. Bumps, such as solder balls 107, are formed on the electrical connections 108. A protection layer 109 covers the electrical connections 108 to expose a portion of the electrical connections 108 for allowing the solder balls 107 formed thereon. Moreover, a buffer film 101 is applied to the bottom surface of the substrate 102.
Devices 100 are generally separated from each other and the rest of the panel by a saw blade cutting along the dash line 110 from the surface having the solder balls 107. The dicing blade is usually made of some hard materials, there are some kinds of blades available commercially: (1) sintered diamond blade, in which diamond particles are fused into a soft metal such as brass or copper, or incorporated by means of a powdered metallurgical process; (2) plated diamond blade, in which diamond particles are held in a nickel bond produced by an electroplating process; (3) resinoid diamond blade, in which diamond particles are held in a resin to create a homogeneous matrix. Silicon wafer dicing is dominated by the plated diamond blade, which has proved most successful for this application.
While saw cutting of wafers and panel is the conventional industry standard, there remain drawbacks with such cutting. Saw blade wear over time. This results in inconsistent cutting quality from when the blade is new and subsequent cutting operations. Consequently, the operator must predict when the blade has reached the end of its useful lifetime. This cannot be predicted accurately. Accordingly, the saw blades may be changed before the end of their useful lives resulting in higher equipment costs than necessary due to premature saw blade replacement. Moreover, saw blades introduce mechanical stresses in the workpiece while sawing, especially at the surfaces of the workpiece. Due to these stresses saw blade may not be used to cut very thin workpiece, such as ultrathin semiconductor wafers. Increasing use of integrated circuits (IC's) technology in microwave and hybrid circuits, memories, computers, defense and medical electronics has created new difficult problems for the industry.
The other drawback of using saw is time consuming. It usually takes 2 to 3 hours to process a wafer. It affects not only the throughput of products, but the cost of processing a wafer and panel.
The cost of the method of dicing wafer using the saw blade is higher due to the blades are not ordinary blades, they are more expensive than general knifes. It costs about US$60 dollars for one dicing blade, and each dicing machine has more than one blade depending on the design.
There is still a drawback by a dicing saw with a saw blade. Each die will have a roughness edges by such method. It is because that the cutting process is an abrasive machining process similar to grinding and cutoff operations, the edges of each die are usually very rough and easy chipping.
In view of the aforementioned, the present invention provides an improved method of separating package for WLP to overcome the above drawbacks.